聊天室显示数据

   webservice    存在新数据时访问数据库，不存在时访问session，减少了对数据库的访问次数

    /// <summary>
    /// 返回开标信息数据集
    /// </summary>
    /// <param name="tenderId"></param>
    /// <returns></returns>
    [WebMethod(EnableSession = true)]
    public List<string> GetInformation(string tenderId)
    {
        string select = "select createtime,operateContent from TB_TenderDirectSeeding where TenderId='" + tenderId + "' order by createtime desc";

        SQLServerHelper SQLHelper = new SQLServerHelper();
        List<string> myList = new List<string>();
        DataTable dt = SQLHelper.SqlGetDataTable(select);

        if (Context.Session["Information"] == null)  //判断session是否为空，session保存要返回的数据集
        {
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                myList.Add("⊙&nbsp;&nbsp;" + dt.Rows[i][0].ToString() + "<br>" + "&nbsp;&nbsp;&nbsp;&nbsp;" + dt.Rows[i][1].ToString());
            }
            SQLHelper.SqlExecute("update TB_TenderDirectSeeding set status='1' where TenderId='" + tenderId + "' and status = ''");

            Context.Session["Information"] = myList;
        }
        else
        {
            if (SQLHelper.SqlGetDataTable("select guid from TB_TenderDirectSeeding where TenderId='" + tenderId + "' and status = ''").Rows.Count > 0)  //判断是否有新数据，有新数据时重新读数据库
            {
                for (int i = 0; i < dt.Rows.Count; i++)
                {
                    myList.Add("⊙&nbsp;&nbsp;" + dt.Rows[i][0].ToString() + "<br>" + "&nbsp;&nbsp;&nbsp;&nbsp;" + dt.Rows[i][1].ToString());
                }
                SQLHelper.SqlExecute("update TB_TenderDirectSeeding set status='1' where TenderId='" + tenderId + "' and status = ''");
                Context.Session["Information"] = myList;
            }
            else  //不存在新数据时 返回session中的值
            {
                myList = (List<string>)(Context.Session["Information"]);
            }
        }
        return myList;
    }